The Mexican-American War is
vitally important to understand because it sets the precedent of a US
president lying, violating clear treaty, and the US stealing resources
at the expense of thousands of deaths of US soldiers, and many multiples
of those deaths of the people we attacked. Then, as today, the
majority of Americans believed their “leaders” in ignorance of the
facts, and without media’s coverage of clear voices like Abraham
Lincoln’s to explain the facts.

The US invaded Mexico in 1846 despite it being a clear treaty violation and upon clear lies of US President Polk: “American blood shed upon the American soil.” The
result of the war was the US taking 40% of Mexico’s land. Although
historians note that freshman member of Congress Abraham Lincoln was/is
correct that the president lied and violated a treaty with criminal
complicity of Congress, both parties’ and media propaganda allowed the
war to move forward without criminal prosecution. The House of
Representatives had enough votes to censure the president for, “a war
unnecessarily and unconstitutionally begun by the President of the
United States,” but not to impeach. Importantly, I’m unaware of any
historian’s rational challenge to this history, despite the lies of
omission you’ll read in corporate media textbooks today.
But don’t believe any expert or me; use your critical thinking
skills. This is as easy as our baseball rule analogy that when a person
knows the rule when a runner is safe or out at first base, there’s no
need to ask anyone. If you know that:

the US had the Adams-Onís Treaty with Mexico
(originally with Spain and formally transferred to Mexico in 1831) in
crystal-clear language regarding the areas of the now Southwest US
(including Texas with all the “border dispute” lands because the Sabine River
between Louisiana and today’s Texas was the agreed border): “The two
high contracting parties agree to cede and renounce all their rights,
claims, and pretensions to the territories described by the said line,
that is to say: The United States hereby cede to His Catholic Majesty,
and renounce forever, all their rights, claims, and pretensions, to the
territories lying west and south of the above-described line; and, in
like manner, His Catholic Majesty cedes to the said United States all
his rights, claims, and pretensions to any territories east and north of
the said line, and for himself, his heirs, and successors, renounces
all claim to the said territories forever.”

Therefore, the US Supreme Law was to forever recognize Texas and the now Southwest as Mexico’s land.

In baseball, you can (and do) say, “I know where first base is. I
know when a runner is clearly safe or out at first base.” In this
“current event” of life and death from our past, you can and should say,
“I know what a treaty means. I know what a border means. I know when
the US is 400 miles over the border that was defined in a treaty that
they’re obviously into Mexico and not on American soil.” You may even
artistically add, “Duh.”
Abraham Lincoln recognized claimed “reasons” for a “defensive war” against Mexico were obvious lies when inspected. Lincoln’s speech as a Member in the House of Representatives:

“I carefully examined the President’s messages, to
ascertain what he himself had said and proved upon the point. The result
of this examination was to make the impression, that taking for true,
all the President states as facts, he falls far short of proving his
justification; and that the President would have gone farther with his
proof, if it had not been for the small matter, that the truth would not
permit him… Now I propose to try to show, that the whole of this, —
issue and evidence — is, from beginning to end, the sheerest deception.”

“Allow the President to invade a neighboring nation
whenever he shall deem it necessary to repel an invasion, and you allow
him to do so whenever he may choose to say he deems it necessary for
such purpose, and you allow him to make war at pleasure. Study to see if
you can fix any limit to his power in this respect, after having given
him so much as you propose. If to-day he should choose to say he thinks
it necessary to invade Canada to prevent the British from invading us,
how could you stop him? You may say to him, — “I see no probability of
the British invading us”; but he will say to you, “Be silent: I see it,
if you don’t.””

I invite you to read Lincoln’s “Spot Resolutions”
for yourself to explain, document, and prove the US president of his
day lying and leading an unlawful war for resources as an example of why
Lincoln is considered to be one of the most brilliant writers in
American history. If passed, Congress would have demanded President Polk
to come before them and respond to Lincoln’s questions.
Henry David Thoreau refused to pay his taxes to support the unlawful
war, and was jailed. Despite Lincoln having all the facts on his side,
because the president, majority of Congress, and majority of the press
wanted this war as an expression of the racist “Manifest Destiny,”
Lincoln didn’t have the votes to pass the Spot Resolutions. In fact,
Lincoln was called “unpatriotic” and “Spotty” in derision by both
parties’ “leadership” and the press.
Lincoln became so unpopular from these intentional lies and propaganda that he had no chance for re-election.
The war killed over 50,000 Mexicans and over 5,000 Americans, and is a
clear historical precedent for US “leadership” to choose lies,
dictatorship, and War of Aggression rather than truth, limited
government under the law, and peace. In addition, the concluding Treaty of Guadalupe Hidalgo
under Article VIII stated property ownership remained under those
current owners. The long history from then to US “ownership” claims
today I’m sure has abundant hypocrisy and crimes.
Although this history of the Mexican-American War is
uncontroversially factual and as far as I’m aware undisputed among
professional historians, corporate media-published high school textbooks
will only state that the causes of war were a “border dispute” and
repeat President Polk’s claims that Mexico invaded the US with “American
blood shed on American soil.”
This is a massive lie of omission and commission to not communicate at least the preceding few paragraphs.
If history texts explained that a US President was the war-mongering
liar that Lincoln explained in his speech and documented in the Spot
Resolutions, and that Congress voted in criminal complicity to shred a
US treaty, lie to the American public about who invaded whom, and be
guilty of war-murdering tens of thousands of human beings, would you look at current US wars from the benefit of that accurate history?

“Progress, far from consisting in change, depends on
retentiveness. When change is absolute there remains no being to improve
and no direction is set for possible improvement: and when experience
is not retained, as among savages, infancy is perpetual. Those who cannot remember the past are condemned to repeat it.”- George Santayana, The Life of Reason, Vol. 1.